Nodal mediated left right asymmetry pathways are critical for multiple aspects of cardiovascular development. Pitx2c, a downstream effector of the Nodal pathways, has been shown to be required for normal outflow and inflow tract development. Moreover, Pitx2c regulates cardiac septation and ventricular growth. Pitx2c is known to be involved in human diseases since it was identified as the gene mutated in Rieger Syndrome I. Importantly, Pitx2c has recently been implicated as a strong candidate for the atrial fibrillation (AF) locus identified on chromosome 4 q25. A firm understanding about the role of Pitx2c in cardiac development and its relationship to AF is lacking. This research program will directly investigate Pitx2c function in cardiac organogenesis using conditional gene inactivation studies and transgenic analysis. We propose to dissect the temporal and tissue specific requirements for Pitx2c in the developing heart by using cre recombinase transgenic methods to precisely inactivate Pitx2c to gain insight into the role of Pitx2c in human disease. Pitx2c has been implicated in human inherited and acquired disorders including Rieger Syndrome and atrial fibrillation (AF). Recent human genetic studies revealed that sequence variations in close proximity to Pitx2 were associated with AF. This study uncovered a role for Pitx2c in the development or homeostasis of the human cardiac conduction system. This research program will perform in depth investigation of Pitx2c during vertebrate development and will therefore provide insight into Pitx2c function with the long-term goal of uncovering therapeutic avenues for human patients. PUBLIC HEALTH RELEVANCE: In this research program, we propose to study the Pitx2c mediated left right asymmetry pathway that is critically important for heart development. Recent work has implicated Pitx2c as a candidate factor for atrial fibrillation in human patients. In the cardiac inflow tract, we will determine the function of Pitx2c in specifying the left atrial pattern. Moreover, in the outflow tract we will investigate the stage-specific function for Pitx2c in OFT growth and remodeling. Lastly, we will use Pitx2c transgenes to investigate the signaling pathways that regulate Pitx2c transcription. Together, these experiments will provide mechanistic insight into Pitx2c in heart development.